That will work; I do it also, with a 3.5mm > XLR cable. In this case, you will be listening to the dac in your AK.
With optical out (also from the 3.5mm port) you will not be listening to the AK`s dac.
There are a thousand explanations on this issue, many by people much more knowledgable than me. Some of them are too technical for me and/or make no sense. You seem to be at the same stage I was at recently, so I will share my understanding. Two things:
1.
For a headphone cable to `be balanced`, there must be 4 wires all the way to the termination. Some `phones combine the wires at some point in the cable, usually at the Y-split or, or at the cups if the cable is 1-sided. Compare these two iem pics: First, my JVC workout specials, the FXZ2000. Notice how there are 2 cables entering the Y-split but only one coming out? One wire from each of the cables have been fused, meaning after the Y-split the cable only contains 3 wires and therefore cannot be `balanced`. A balanced connector can be attached, but this would only be done for connectivity, not to modify SQ.
This is my CKR9 :
You can see the two cables from the drivers, each with 2 wires, continue all the way to the 3.5mm plug. The cable housings are simply linked together by the Y-split; the internal wires are not affected This cable can be re-terminated to `real` balanced, with iimpact on the SQ. (Whether or not you can hear that impact is of course a never-ending debate).
You just need to confirm if your `phone cable has 4 wires all the way to the plug, or not.
2.
The second point I learned is that the 2.5 TRRS plug is not uncommon in other areas of electronics, however AK`s wiring pattern apparently is uncommon. So, you really have to confirm that the cable guy knows the correct wiring scheme. You could damage the AK if the wiring is wrong, I think. This:
Good luck.
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